Fasteners comprising releasable clips for use on garter belts, suspenders, diapers, mittens, etc., have been known for over thirty years. Reference is made to Hawie U.S. Pat. Nos. 2,219,991 and 2,837,806, for example.
Conventional fasteners of this type comprise parts which are stamped from metal, including a base plate having an eyelet, wire loop or pin for attaching the fastener to one material, such as a suspender strap, a diaper or an elastic strip. A clamping jaw plate is pivotally-attached to the base plate and an actuating plate or lever is pivotally-attached to the base plate, overlying the clamping jaw, and adapted to move against the clamping jaw and cause the latter to move towards and releasably lock in closely-spaced parallel position relative to the opposed face of the base plate. The base plate and the clamping jaw were formed to have cooperating fabric-gripping teeth which close together to penetrate and grip the flexible fabric material over which the clip is placed and locked.
Conventional fastener clips of this type continue to be in widespread use, but they do have disadvantages, particularly when used in association with flexible fabrics which are thin, slippery or prone to tearing or to running. Unless the gripping teeth are sharp and tightly engaged, they will not hold a thin and/or slippery fabric such as silk or synthetic woven fabrics or plastic films against strong pulling forces. However, such sharp and tight teeth can cut the fabric, causing tears and runs. The teeth penetrate the fabric to provide spaced anchor points, and the pulling force against the fabric is concentrated at these anchor points to produce spaced areas of stress, each of which is isolated from the others so that no cooperative result is obtained.
It has been proposed to avoid the use of the conventional metal gripping teeth in clip fasteners by providing cooperative plastic gripping members on the opposed surfaces of the base plate and the clamping jaw plate, the gripping members having plastic teeth which come together to clamp a flexible fabric when the fastener is locked. While such plastic gripping members have smooth plastic teeth which do not cut through a flexible fabric in the same manner as the conventional sharp metal teeth, they have the important disadvantage of greater slip-permission and reduced holding power relative to thin and slippery flexible fabrics. Since the smooth plastic teeth do not penetrate the fabric to any substantial degree, they do not provide strong anchor points and, therefore, while a strong pulling force on the fabric will not usually result in tears or runs, it will cause the fabric to slip or creep from between the plastic teeth and out of engagement with the fastener clip.